feat(standup): standup automatique hier/aujourd'hui/blocages (issue #6)

format_standup_text + _standup_data (journal de la veille, focus
du jour, vieillissantes QA/Révision); page /standup copiable,
/api/standup; inclusion optionnelle au briefing ntfy
(KANBANTE_BRIEFING_INCLUDE_STANDUP).

app/templates/sprint.html

@@ -16,6 +16,7 @@
             <a href="/board/{{ full_name }}" class="nav-pill">📋 Board</a>
             <a href="/today" class="nav-pill">🌅 Aujourd'hui</a>
             <a href="/forecast" class="nav-pill">🔮 Prévisions</a>
+            <a href="/rules" class="nav-pill">⚙️ Règles</a>
             <button type="button" class="nav-pill palette-trigger" title="Palette de commandes (Ctrl+K)">⌨️ Ctrl K</button>
         </nav>
     </header>